Development discussion for DB Browser for SQLite (previously SQLite Browser)
https://bit.ly/submitBug
I have a question on javascript
This is primarily a support chat area for DB4S which is a database management tool. I don't believe the users familiar in it are also familiar with Javascript.
Can I get Gitter to send me an email for responses?
If you click the settings (assuming you're on the desktop browser version) there are notification options in there. Click 'Notifications' and not 'Settings' (once you've clicked the settings icon, I mean...)
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'String', "String" and String when running any query? I noticed they're all work when asking data from the DB, using those DB names and row names.
Carlos - You have a number of SQL engines (mySQL, Microsoft, etc) and SQLite tries to help out by being compatible with them as they all work a little differently. This means you could use an apostrophe or quote but SQLite tries to work out what you really mean.
Generally, strings are enclosed in apostrophe's, so select from table where field1='Fred' means it'll find data that matches the string 'Fred'. If you use field1="fred" then it tries to find a column (or table, view, etc) that matches "fred". BUT, if it doesn't find one, SQLite thinks, "aah, did you mean 'Fred'?" so that might also work. You shouldn't rely on these though, and should ideally get the quotation marks correct.
Ideally, all fields and tables should be a singular word without spaces. So don't call a table "table 1". If you do, you have to put quotation marks around it (not apostrophes) when using it in SQL - eg, select from "table 1" where field1='Blah blah'
Does any of this make any sense?
I don't have any issue with a 5GB database.
On the "Browser Data" tab, the row count is displaying after a few seconds at the bottom and after that it is frozen with the bottom right message "Busy (reading rows)".
I have set the prefetch value to 255, but it doesn't help.
CPU usage is high but I still have enough RAM available.
Can somebody tell me if I have missed something ? I don't want to re-open the issue and bother the developers if I made a mistake... Thanks !
I have set the prefetch value to 255
I don't believe this helps in this instance - it only helps when scrolling through the table - it'll grab 255 records at once. Usual values are ~50,000 so it grabs 50,000 records in a go.
Without being rude, why are you using the data browser tab for such a large number of records? At 100 GB, this is going to be a lot of rows ... why would you want these all displayed? Usually, once the data is in the database, you perform actions on that data - how many records with a value of X in field Y, how many records with a value of Y in field Z, etc. You can perform that using SQL - eg, you don't view all million rows to find out there are a million rows. If you're scrolling through data, you can use 'limit' to make this manageable.
In my eyes, this is like opening a 900,000 page word document, then wondering why it takes a while to scroll up and down. Some will argue that DB4S should handle 80 million rows, but I fail to see the advantage of viewing this on screen... (just my personal opinion, of course!)
I don't want to re-open the issue and bother the developers if I made a mistake...
I would recommend opening a new issue, and making reference to the other issue - don't open an older one. The older one refered to a different version of DB4S, plus it will notify the original poster, when really you need your own new shiny issue that belongs just to you. Open it up as it might highlight something wrong with DB4S that can be fixed.
There is already an open issue where the number of rows visible in the grid is limited - possible due to the control we use in DB4S. This comes back to my (waaaaaaaay too long) point above that displaying a large number of results is a nuts thing to do anyway.
You can't compare DB4S to emacs - it's like my example above - Word wouldn't open a 90,000 page document.
An SQLite database is a million times better than a CSV for querying - a database is built for querying, while a CSV isn't.
The 'browse data' tab is designed for small tables as it loads every record and relies on a filter. What would be better (for your example) is a grid asking 'what do you want to look at?' (eg, a numeric range or date range) so you can scroll through that. Again, a subset, rather than the complete table.
I am using (abusing ?) it a bit like I would use Excel to browse/filter/display a table with a lot of data.
Similarly for SQLite file, I wanted to have a peek without having to (manually) type a query to display the first hundreds of lines.
But if DB Browser for SQLite is really built in a way to forcibly load the entire database
Not intentionally it doesn't - there is a lot of work to make it as smooth as possible (the reason for the 'prefetch block size') but the first thing it has to do is work out how many rows the table has, so it does a 'select count(*) from table', and it's this that can hammer large databases. Even with an index, a 100 GB database is going to take time to get this figure.
Anyway the reason for the freeze is not the process which counts the number of rows then, because the freeze is happening after the count is displayed.
How do you manage to count the number of rows so quickly ?
I knoweth not. I tend to steer clear of the DB4S code ... here be dragons. I know a lot has gone into making it optimised though... tweaks here and there, etc.
The application log in DB4S might assist in working out where the freeze is occurring.
If you don't need to edit records, the 'execute SQL' tab is useful to grab records, and that should be speedy. The grid is 'read only' which isn't always great.
But I thought it was impossible to have an accurate count of the number of rows quickly (i.e. faster than "select count(*)" which is taking ages
Depends on the version of SQLite. I know SQLite itself (so not DB4S) has sexy internal methods to make this query fast. Depending on the table contents, it can be quicker doing a 'select (1)' rather than a 'select (*)' which would pull in a load of data, only to discard it.
The next query is "SELECT 'rowID', from table LIMIT 0; 253" and the GUI is frozen from there (the first lines does not appear). I tried executing this query outside and it is returning the result instantly.
So there is something wrong around this last query but no means for me to debug this further (nothing in the Error Log as well).
So there is something wrong around this last query but no means for me to debug this further
That's useful to know - thanks for digging that out.
I would have suggested raising an official issue for it, as it's something we'd like to get fixed, but development has ... er, kinda stalled at the moment and the issue count is >470, so it's going to get lost in the noise for a while, so won't get solved in the short-term.
... and that's not even counting the SQLite backend's processing time for running queries, though indexes can definitely help there. :)
